Deliveroo, founded by two Americans in London in 2013, announced on Friday a $575 million funding round led by Amazon. Shares in Just Eat, a pioneering U.K. website for ordering takeout food that now competes with Deliveroo, fell almost 10%. Shares in
Delivery Hero
DHER -1.17%
and
Takeaway.com,
TKWY -1.61%
which offer similar services to Deliveroo in other markets, also cratered.

Whether these two players use their riches to eat each others’ lunches, or those of other couriers, is hard to predict in a fast-moving industry. Eventually, the market is likely to be reordered by deals. Uber Eats tried to take over Deliveroo last year but couldn’t agree on valuation.

The mergers that do occur in this industry benefit shareholders a lot: When Takeaway.com and Delivery Hero agreed to combine their German businesses last December, the shares jumped 28% and 10% respectively. That is the risk for those looking to bet against players like Just Eat, which still has a strong market position in the U.K.

America's love for take-out is spurring a boom in food delivery startups. But what's convenient for customers may not be good for restaurants. Here's why.

That said, mergers are less likely while the money to compete is flowing so freely. Instead, the cash will likely subsidize further rapid growth. Delivering restaurant meals to homes spares consumers the chore of cooking even if they want to eat in. This sector is as hot in the U.S.—where
Grubhub,
DoorDash and even Amazon Prime Now compete with Uber Eats—as it is in Europe and elsewhere.

The real losers of this trend could be the retailers that sell groceries. Food that would once have been bought in stores and cooked by consumers is being bought and cooked by restaurants.

The growth of meal delivery has the capacity to transform much more than the traditional takeout industry.

WSJ opens select articles to reader conversation to promote thoughtful dialogue. See the 'Join the Conversation' area to the rightbelow for stories open to conversation. For more information, please reference our community guidelines. Email feedback and questions to moderator@wsj.com.